Climatology of surface meteorology, surface fluxes, cloud fraction, and radiative forcing over the southeast Pacific from buoy observations

Virendra P. Ghate, Bruce A Albrecht, Christopher W. Fairall, Robert A. Weller

Research output: Contribution to journalArticle

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Abstract

A 5-yr climatology of the meteorology, including boundary layer cloudiness, for the southeast Pacific region is presented using observations from a buoy located at 20°S, 85°W. The sea surface temperature and surface air temperature exhibit a sinusoidal seasonal cycle that is negatively correlated with surface pressure. The relative humidity, wind speed, and wind direction show little seasonal variability. But the advection of cold and dry air from the southeast varies seasonally and is highly correlated with the latent heat flux variations. A simple model was used to estimate the monthly cloud fraction using the observed surface downwelling longwave radiative flux and surface meteorological parameters. The annual cycle of cloud fraction is highly correlated to that of S. A. Klein: lower-tropospheric stability parameter (0.87), latent heat flux (-0.59), and temperature and moisture advection (0.60). The derived cloud fraction compares poorly with the International Satellite Cloud Climatology Project (ISCCP)-derived low-cloud cover but compares well (0.86 correlation) with ISCCP low- plus middle-cloud cover. The monthly averaged diurnal variations in cloud fraction show marked seasonal variability in the amplitude and temporal structure. The mean annual cloud fraction is lower than the mean annual nighttime cloud fraction by about 9%. Annual and diurnal cycles of surface longwave and shortwave cloud radiative forcing were also estimated. The longwave cloud radiative forcing is about 45 W m -2 year-round, but, because of highly negative shortwave cloud radiative forcing, the net cloud radiative forcing is always negative with an annual mean of -50 W m -2.

Original languageEnglish (US)
Pages (from-to)5527-5540
Number of pages14
JournalJournal of Climate
Volume22
Issue number20
DOIs
StatePublished - Oct 2009

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radiative forcing
surface flux
meteorology
climatology
cloud radiative forcing
cloud cover
latent heat flux
advection
surface pressure
downwelling
annual cycle
wind direction
diurnal variation
relative humidity
surface temperature
sea surface temperature
air temperature
boundary layer
wind velocity
moisture

ASJC Scopus subject areas

  • Atmospheric Science

Cite this

Climatology of surface meteorology, surface fluxes, cloud fraction, and radiative forcing over the southeast Pacific from buoy observations. / Ghate, Virendra P.; Albrecht, Bruce A; Fairall, Christopher W.; Weller, Robert A.

In: Journal of Climate, Vol. 22, No. 20, 10.2009, p. 5527-5540.

Research output: Contribution to journalArticle

Ghate, Virendra P. ; Albrecht, Bruce A ; Fairall, Christopher W. ; Weller, Robert A. / Climatology of surface meteorology, surface fluxes, cloud fraction, and radiative forcing over the southeast Pacific from buoy observations. In: Journal of Climate. 2009 ; Vol. 22, No. 20. pp. 5527-5540.
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